The histological characteristics of 9 cases of granular cell turners (GCTs)
observed in B6C3F(1) mice were examined to deter mine their cellular origi
n. Seven of the 9 cases were found in the uterus and other 2 cases were in
the subcutaneous tissue. Tumor cells had abundant granules in the cytoplasm
which were stained with PAS and were resistant to diastase treatment. Ultr
astructurally, the granules were identified as lysosomes. The cell surface
had cytoplasmic processus showing interdigitation with adjacent cells. A ch
aracter feature of the tumor cells was the presence of a desmosome-like str
ucture on their cell surface but no basal lamina was demonstrated. Although
GC-Ts have been considered to be derived from Schwann cells on the basis o
f their ultrastructural features and S-100 protein-immunopositive findings,
the absence of basal lamina in the present cases may raise a controversy a
s to their origin.